A backlight module is an essential component of LCD devices. The backlight module usually includes a light guide plate, an LED array and a backplane, wherein the light guide plate is in parallel and fixed together with the backplane, the LED array is arranged between the light guide plate and the backplane. In the prior art, the light guide plate and the backplane are assembled generally by engaging the light guide plate to the backplane via a riveting column, or by filling a rubber pad between the light guide plate and the backplane so as to fix the light guide plate through the interference fit. However, the light guide plate, because of its prominent expansion attribute, has not only the thermal expansion attribute but also the hygroscopic expansion attribute, making both of the above two assembly methods have defects. If the light guide plate is fixed by the riveting column, with the riveting column made of a rigid material, when the light guide plate is expanded due to heat or moisture, because its expansion is subjected to restriction of the riveting column, the riveting column is hard to be pushed to move with the expansion, and therefore expansion cannot be released evenly, which easily results in an inhomogeneous deformation, making the light guide direction have deviation and distortion. If a rubber pad is used for fixing the light guide plate, because there is a nonlinear relationship between the elastic force and the degree of deformation generated by the rubber material, when the light guide plate is expanded to compress the rubber pad, the elastic force applied to the light guide plate will become increasingly large with the degree of compression, and thereby the amount of expansion that can be released by the light guide plate is not much, while a greater elastic force generated by the rubber pad may cause serious deformation on the stress portion of the light guide plate. Thus, with the light guide plate fixing structure of the prior art, the LCD device will suffer a reduced display effect inevitably during application because of expansion of the light guide plate. Therefore, this fixing structure needs to be improved urgently, so as to improve the product quality and enhance the user experience.